Specimen Grips with Two-Stage Clamping for Safe, Reliable Dynamic Testing of Wire Strands as per ISO 15630-3 

Clamping the specimen in fatigue tests on strands as per ISO 15630-3 represents a particular challenge, as jaw breaks can occur relatively easily. The gripping force causes a load to be superimposed on the dynamic test load in the clamping area, which can lead to premature specimen failure. Therefore, for classic tensile specimens made of solid material, the ends often have larger cross-sections to ensure that the specimen breaks in the free portion between the specimen grips. With wire strands it is not so simple. To obtain correct test results, extensive specimen preparation, such as sealing, is required.
Wire strand testing

With specimen grips developed specifically for wire strand testing, ZwickRoell now offers the option to test strands without having to use specially attached clamping elements. This development substantially reduces the required handling, time, and expense for the user.

The grips feature hydro-mechanical and straight mechanical clamping. The latter comprises a conical sleeve into which each end of the strand is fed together with a counter-cone and clamped. Most of the gripping force is applied in this manner. The remaining portion still needed for the respective test is supplied by classical hydro-mechanical clamping via jaws. The combination of these two gripping principles enables the gripping force to be applied in such a manner that jaw breaks are eliminated and wire strands can be tested without being pretreated.

The specimen grips are extremely flexible and can be used for a wide range of applications. The variably adjustable hydraulic gripping force can be easily changed from test to test by regulating the oil pressure accordingly.

The specimen grips (Fmax 500 kN) are typically used with an HA series servo-hydraulic testing machine.